What John Green is most well known for is being the "older half" of the 2007 Brotherhood 2.0 project. Inspired by Ze Frank, John and his younger sibling, Hank Green, gave up textual communication with each other for an entire year. Instead, they spoke primarily through YouTubevlogs, under the username vlogbrothers. The show became widely known after Hank Green posted a song about the last Harry Potter book, "Accio Deathly Hallows." A huge fanbase grew up around the show, and its devotees became known as Nerdfighters.

In the real world, John Green has a wife named Sarah (known mostly as the Yeti by Nerdfighters due to her rare appearances) and a son, Henry. He continues to make regular videos and host Nerdfighter Gatherings in addition to writing books.